This invention relates to a passive optical transponder and, more particularly, the invention is concerned with providing a transponder wherein the natural ultra-violet light from an interrogator is focused on a phosphor which gives off visible light during its excitation cycle. The response light is a different color from the interrogation light and can be used as a means for location and identification of friendly forces.
In general, communication between two remote sites is presently carried out by means of voice communication through the use of telephone or radio, or by Morse code light signals. In each of these systems, various situations arise which make their use highly disadvantageous or impossible of operating, such as when transmitting classified communications and where ground forces are being tracked by a tactical air support team. Also, the problems of frequency allocation in regard to radio broadcasting and the problem of wires when involved with telephones limit the practical capability of these systems under certain conditions. In addition, each of the above known systems for intelligence communication are subject to being monitored by those for which the communications are not intended, and may be jammed or intercepted by undesirable recipients while also requiring considerable set up time and maintenance.
Thus, there is an urgent need in the art for a simple and reliable identification and communication system which is not subject to interception and jamming and which can be operated under adverse conditions by semi-skilled personnel without the requirements of expensive and time-consuming set up and maintenance problems.